Hello dearest reader,
This week I learned how to use the waterjet cutter and how to post-process metal! The assignment was to make two identical diamond shaped pieces.
I decided I wanted mine to have a cutout of my childhood favorite animal, a monkey, so I found an SVG file on The Noun Project, loaded it into Adobe Illustrator, circumscribed it in a diamond, and sent it to the waterjet cutter to cut. I had some trouble differentiating between a shape and a path in Illustrator; in fact, the first time I sent my piece to the waterjet cutter, the computer was not able to identify which section to cut. I went back to my file and tried to apply the Shape Builder tool, and the next time I used the waterjet cutter, with a bit of selecting/deselecting unwanted lines, I overcame the trouble I’d been having.
Below, you can see the file prepped for waterjet cutting, the lead in and machine path:
I made sure the machine cut out the monkey interior before the diamond exterior; in case the diamond piece moved around when detached from the base sheet of metal, I didn’t want the monkey cut to be in the wrong place. Below, you can see my piece as it was being cut.
As you can tell, the metal pieces are pretty dirty after being submerged in the waterjet cutter, so I cleaned my pieces with soap and water in the wet lab. Shown in the photos below, the scrubbing didn’t get it perfectly clean, but there was definitely improvement!
Before cleaning (left), after cleaning (right)
On to post-processing! I decided to round the edges of my diamonds by filing them. This wasn’t really an exact science, I just kept at it until it felt round. Or, in the case of the second diamond, until I felt it matched the first.
For the rest of my post-processing, I originally experimented with a scrap piece of metal to see what I thought looked the best. On the metal piece below you see three different sections:
The leftmost was wire-brushed and then sandblasted.
The middle was only sandblasted.
And the rightmost was sandblasted and then wire-brushed.
The first two don’t look that different from each other (the left looks a bit brighter if you look really hard), but wire-brushing after sandblasting certainly made a difference!
I thought seeing multiple different post-processing methods on one piece was pretty cool and I liked the unpainted metal look, so I decided to have my final product be a combination of these post-processing methods.
I sandblasted both of my diamonds on both sides. I had a bit of trouble with the sandblaster because the light wasn’t working, so it was really hard to see into the machine and visualize what was happening. I tried to solve this by placing my phone flashlight on top of the viewing glass, but that wasn’t that effective of a solution. I ended up just opening and closing the machine door over and over again to see what was going on. I made sure to sandblast the parts that were dirty for a while longer to give the diamonds an even color. Yet, I still noticed some small dark spots in different areas on my diamonds that I wasn’t really fully able to get rid of.
In the picture below, you can compare the diamonds pre- and post-sandblasting.
Sandblasted (left) vs original (right)
Next, I taped off portions of my diamonds with painters tape, and wire-brushed two of the four quadrants on the front face. I intentionally chose to wire brush the sections that had more of the unwanted dark spots after sandblasting, as the wire brush was successfully able to remove those. I also made sure to only wire-brush in one direction so I wouldn’t accidentally brush under the tape and ruin my straight lines. Unfortunately, you can spot a difference in how exact the line between wire-brushed vs only sandblasted is between my two copies and while I initially tried to fix this, I was worried I would accidentally brush over into the other quadrant, which I felt would look worse than what I already had, so I left it as is.
Taped off section to wire-brush
Wire-brushed quadrant once tape was removed
This is the final product, I’m really happy with how it turned out!
Cost Estimations:
Labor: 3 hrs * $10/hr = $30
Wage based on OEDK Lab Assistant pay
1/16″ x 12″ x 24″ Aluminum Sheet: $16.97
https://www.amazon.com/16-Aluminum-Plate-5052-Gauge/dp/B084KLCVN4
Waterjet Time: $24/hr * 1hr = $24
Estimated from reported cost of abrasive * 4.33 (since abrasive was 75% of total hourly cost)
https://www.esabna.com/us/en/education/blog/how-much-does-waterjet-cutting-cost.cfm
Sandblaster Time: $26.50 to rent for a day
https://www.rsmeansonline.com/References/FMR/2015/Equipment-Rentals-2015.pdf
Metal File: $7.97
https://www.homedepot.com/p/Nicholson-8-in-Handy-File-06601N/202982703
Wire brush: $2.96
Adobe Illustrator: $20.99/month *1 month = $20.99
https://www.adobe.com/creativecloud/plans.html
Total Cost: $129.39
Note: this cost value is so high because the calculations involved purchasing all of the materials/hand tools involved and renting out all of the power tools for significantly longer than actually used because it was the smallest time increment I could find online. Of course, using a shared makerspace like the OEDK is a much better use of resources.
